Keep in mind, a fellowship just means more money for less work. Which is nice, of course! But it does NOT mean you will have any "edge" when it comes to choosing research, graduating, finding a job after graduation, etc. In fact, most fellowships expire after 1-5 years, at which point you'll just be a normal grad student.
In any case, after you graduate, your fellowship means absolutely nothing. So go by reputation! I would say you should *always* choose the school with the better reputation unless:
1) Your career plans don't require a "prestigious" Ph.D., ie you want to be a high school teacher
2) There is no real difference in reputation, both schools have similar rankings/opportunities
3) The more reputable school seems so miserable that you don't think you would do good work there (this is very rare, but sometimes comes up if your gf/bf would be in a different city, or you don't get offered financial support at one school, or something along those lines)
In short, TA at top 5, no brainer. Best of luck!